1. Field of the Invention
This invention relates to a cylindrical fuse holder for accommodating a fuse tube for use in an electric power source unit of electronic equipment.
2. Description of the Prior Art
There has been generally known a prior art cylindrical fuse holder formed in a cylindrical shape on the whole by uniting a holder body and a cap between which a fuse tube is held, as shown in FIG. 9. To be more specific, this conventional cylindrical fuse holder comprises the holder body 1 formed in a cylinder with a bottom by molding, and the cap 2 formed by molding for closing the opening of the holder body 1. Within the holder body 1, there are mounted a bottom contact piece 3 on the bottom of the holder body 1, and a side contact piece 4 attached on the inner circumferential surface of the holder body. Within the cap 2, a conductive metal cylinder 5 is integrally formed by insert-molding and has its leading end extending inside the holder body 1. In the metal cylinder 5, there are mounted a socket 7 having a pair of pinch pieces 7a and 7b between which one of the terminal portions of the fuse tube 6 is held, and a fuse tube pressing spring 8 formed of a coil spring and inextricably disposed for exerting the fuse tube 6 outward. The outer peripheral surface of the outwardly protruded part of the metal cylinder 5 placed in the cap 2 has a male screw, and correspondingly, the inner peripheral surface of the annular part 4a of the side contact piece 4 has a female screw. By engaging both the screws, the holder body 1 is closed with the cap 2.
To retain the fuse tube 6 within the cylindrical fuse holder, upon removal of the cap 2 from the holder body, one of the terminal portions of the fuse tube 6 is first inserted into the metal cylinder 5 to hold the fuse tube 6 between the pinch pieces 7a and 7b of the socket 7, and then, the leading end of the metal cylinder 5 is thrust into the annular part 4a of the side contact piece 4. Thus, the fuse tube 6 is retained in position within the cylindrical fuse holder in such a state the other terminal portion of the fuse tube 6 is brought into press contact with the bottom contact piece 3 by the spring 8, establishing an electrical connection between the other terminal portion of the fuse tube 6 and the contact piece 4 through the spring 8 and the metal cylinder 5.
The conventional cylindrical fuse holder as described above can assure high stability because the holder body and the cap are steadily screwed. However, since both the principal components with having the screws are formed of metal, they must be made by cutting, resulting in increasing the cost of production and the number of component parts. As a result, the conventional fuse holder thus produced has a disadvantage of being rather expensive.
Furthermore, the conventional fuse holder is disadvantageous in that, in the work of screwing the cap into the holder body, the side surface of the metal cylinder protruding from the cap is exposed between the cap and the holder body, thus involving a danger of receiving an electric shock if an electric current flows the fuse.